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Precipitation, Fog and Pollution

Precipitation, Fog and Pollution. L/O: to be able to describe how precipitation, fog and pollution vary between rural and urban areas. What is an anticyclone?. Air is sinking – not rising (pressure?) Lack of fronts means wind may be light Conditions: dry settled and bright

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Precipitation, Fog and Pollution

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  1. Precipitation, Fog and Pollution L/O: to be able to describe how precipitation, fog and pollution vary between rural and urban areas

  2. What is an anticyclone? • Air is sinking – not rising (pressure?) • Lack of fronts means wind may be light • Conditions: dry settled and bright • Summer: Hot dry weather • Winter: Clear skies, cold nights and frost • In winter also related to fog because cold forces moisture to condense at low altitudes

  3. Precipitation • How is it different? • More thunder storms • More convective storms of greater intensity • Why?? • UHI generates convection • High rise and mix of building heights = more turbulence and vertical motion • Water vapour from industry • Hygroscopic nuclei = raindrop formation • Friction from urban area slows fronts • Also increase of PPT down wind • SNOW???

  4. Fog • Humidity in urban areas is lower (why?) • At night urban areas retain humidity (as air doesn’t cool so fast) • Pollution particulates are hygroscopic • Through the day water attaches to pollution particles • As the air cools at night, fog forms • Especially in river valleys (more water vapour)

  5. Fog continued • More fogs in urban areas (100% more) • Last longer • More intense • Lower visibility • Lower sunshine levels in cities.

  6. Pollution • Suspended particulates • Burning fossil fuels • V small (micro metres) • Spoil buildings • Act as carcinogens • Fog/smog • Sulphur dioxide (SO2) • Haze, acid rain, respiratory problems, damage to plants

  7. Pollution cont… • Oxides of Nitrogen (NOx’s) • Weathering of buildings, rain, haze • Carbon Monoxide (CO) • Heart probs, headaches and fatigue • Photochemical oxidants (Ozone O3 and peroxyacetal nitrate PAN) • Smog, plant damage, headaches, eye irritation and chest pains)

  8. Today • Write a definition for hygroscopic • How is precipitation different in rural and urban areas? Why does this occur? • Why is fog more common in urban areas? • What are the major pollutants in urban areas and what effects do they have? • How does air pollution vary with the time of year?

  9. Why is there a greater incidence of fog in urban areas? (7 marks) • How are precipitation and fog related to particulate concentration? (8 marks)

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